High speed trip device for electric circuit breakers



1953 MASATOSHI KUWAYAMA 2,662,136

HIGH SPEED TRIP DEVICE FOR ELECTRIC CIRCUIT BREAKERS Filed March 14,1951 INVENTOR fins/970s, 111w yam;

BY W, M I; fimsA rs Patented Dec. 8, 1953 HIGH SPEED TRIP DEVICE FORELECTRIC CIRCUIT BREAKERS Masatoshi Kuwayama, Taga, Japan, assignor toHitachi Limited, Chiyoda-Ku, .Tokyo, Japan Application March 14, 1951,Serial No. 215,505

3' Claims.

This invention relates to an improvement in a high speed tripping devicefor electric circuit breakers.

It has heretofore been known in electric circuit breakers that thecircuit should be cut-off as quickly as possible in order to prevent thearcover between the contacts and to avoid damages of elements. For thispurpose, various quick tripping devices have been proposed, but most ofknown devices cons sts merely of a combination and special arrangementof a number of levers and link mechanisms so that they are complicatedin construction and heavy in operation owing to frictions between manyworking parts.

In accordance with the present invention, the above mentioned defectsare overcome by us ng a pair of cooperating rollers between the trippingelements and by adequately selecting the slope of the working surface ofthe tripping lever For a better understanding of my invention,

reference is taken to the accompanying drawing, in which,

Fig. 1 is an elevation showing an arrangement of rollers and cooperatingelements taken for the explanation of the principle of operation of thehigh speed tripping device of this invention,

Fig. 2 is an elevation showing a construction and arrangement of thepresent device when the, circuit breaker is closed,

Fig. 3 is a view similar to Fig. 2 when the circuit breaker is opened,

Fig. 4- is a side view of the roller supporting mechanism, and

Fig. 5 15a partial elevation showing a construction of heretoforeordinary tripping device.

Now referring to Fig. 1, which shows the principle of the trippingmechanism of this invention, R represents a pair of tripping. rollers; Aand B designate inclined plates acting on the rollers, and S- is astrip. placed between the rollers. If an external force P isv applied toeither one or both of the inclined plates A and B in the direction of P,the rollers R will be turned in the direction as shown by the arrows a,thereby the strip 8 is forced out in the direction of the arrow I) andas the result the rollers are shifted by rolling in the same directionas the movement or the strip. If the external forces P are the same, theshifting force Q acting on the strip S through the rolling motion of therollers will be proportional to sine 0 when the angle 0 between theinclined plates A and B is small. Owing to the fact that the operationbetween members of the mechanism consists entirely of the rollingfriction, it is possible to reduce the value of sine 0 to less than ,5If the strip S is held stationary by some means, the coefficient offriction between the strip and the rollers may be assumed much greaterthan the value of sine 0 so that the rollers R can be prevented fromrolling in the directions of the arrows at and be held stationaryagainst the external forces P.

The principle of the roller mechanism is utiliaed for the tr ppingdevice of electric circuit breakers according to this invention. Figs. 2to 4 illustrate a preferred construction and arrangement embodying thisinvention. Referring to these figures, i represents a link connected toan operating member of a circuit breaker (not shown), which is normallyforced in the direction of W by the bias of opening force when thecircuit breaker is in the closed condition. 2 is 'a movable latch memberor latch lever pivoted at one end and connected at its middle to thelink i, the free end of the lever 2 forming an inclined surface A whichengages on the tripping roller R. 3' represents a frame work forsupporting the rollers R, the axis 4 of each roller engaging in aguidegroove 1 of the frame 3 and being held by a spring 6 which is stretchedbetween the lug pin 5 and the roller axis The frame 3 is fixed to thebase plate 8. S is an adjustable stopper pivoted at one end and fixed atthe other end to the base frame 8 by means of adjusting screws l0 and H.The stopper 9 is provided with an inclined surface B acting against oneof the rollers R and the inclination of the surface may be adjusted bythe screws l0 and H.

[2 represents a stationary core of a tripping electromagnet; I3 is itsmagnetic bridge; it is a holding coil; 95 is a trip coil wound aroundthe magnetic bridge IS, and it represents a movable iron piece whichis-connected with the strip S at its upper end and engages at the loweredge with the corresponding edge F of a non-magnetic element It whichisfixed to the core it. it represents a tension spring acting to pull upthe movable iron piece it. The line X-X illustrates the locus ofmovements of the free end of the latch lever 2.

Fig. 2 shows the position of operating memhers of the present devicewhen the circuit break- .-.1' ii a closed condition, wherein the holdcothe trip magnet is energ zed so that the rnov-.. -e piece 58 may bepulled by means flux 1 passing through the iron piece ii to fix thestrip S, thereby preventing the rollmovement of the rollers B so thatthe turnof the latch lever in the direction of W can be prevented.

Now if the trip coil i5 01 the electro-magnet is energized, the link Iis shifted from the path of the iron piece it toward the magnetic bridge53 and releases the iron piece lfi.

the result, the strip S can no more prevent the bias of turning of therollers B, and the latter are shifted downwards by rolling in accordancewith the operating force of the latch lever 2 and the strip '55 locatedbetween the rollers will be shifted downwards at a speed twice that oithe rollers. Thus the lever 22 interlocked by means of the rollers isreleased and the circuit breaker is allowed for circuit openingoperation. After the completion oi the above operation the mow ableiron. piece [5 is pulled up by the spring I8 and meanwhile the rollers Rare pulled up by the spring ii, thus all parts are re-set to thepositions as shown in Fig. 2. In re-closing the circult breaker, thelatch lever 2 forces down the rollers R by its free end and moves to theinterlocking position shown in 2 and is re-set to that position by therollers.

5 represents an example of heretofore usual trip ing mechanism taken forthe comparison with this invention, wherein 2| designates a link pivotedat 22; 23 is bell-crank lever pivoted at M, and 25 is an iron piecepivoted at 25 serving the tripping iron core of a trippingelectr0-magnet 7!? having a trip coil 28. In such a mechanism, themovement of the latch lever 2 in the direction of W is prevented by aroller R put on the top of the lever 2 I, which engages one end of thebellcrank lever 23, the other end of the later being engaged with theiron core 25. Owing to a number of pivots, levers and links andmulti-stage operations, there occurs frictional resistances betweenco-operating members in each stage. In order to avoid the uncertainty ofoperation, it is necessary to selectthe smaller reduction ratio onestage so that a longer time is required for the effective trippingoperation with. such multi-stage mechanism due to the increased time.Thus it is actually difficult to att the object of h' h speed trippingoperation for C uit breaker of a large capacity.

On the other hand, according to the tripping device this invention thereis no part causing a large frictional resistance except a small roilingfriction and it is possible to establish a high reduction ratio of onestage such as to & Moreover the operating parts can be made very li htsince there is no intermediate members such as fixed pivotal and linklevers and the like. According to the results of comparative testsefiected with the heretofore trip mechanism and the present device orthis invention adopted for a circuit breaker of 161 K. V., the formerrequired more than 0.02 second for the starting of latch lever after themovable core has started, while the latter showed it required only 0.002second. Another advantage of the present device is that there occursabsolutely no slip between the cooperating members since the coefficientof friction between the strip S and the rollers R is much greater thanthe coefilcient oi slope between the surfaces A and )3.

Further advantage of the present device is that the weight of workingparts and the friction between them can be reduced to the minimum,thereby effecting a desired high speed tripping operation.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

l. A high speed trip device for electric circuit breakers, comprising apair of cooperating rollers having their axes in parallel spacedrelation, opposed inclined surface members biasing said rollers to rollin opposite directions, at least one of said members being a latch leverof the circuit breaker, a strip contiguous between said pair of rollersand connected with a movable armature of a tripping electro-magnet, saidarmature acting to prevent the bias of said rollers from operating saidlatch lever, and said armature operable upon energization of saidtripping elect1'o magnet to allow one of said rollers to move fromrestraining engagement with said latch lever, whereby the circuitbreaker is allowed to operate.

2. A trip device according to claim 1, including means for adjusting theangle of inclination of the inclined surface of the other of saidmembers.

3. A high speed trip device for electric circuit breakers, comprising alatch lever of the circuit breaker pivotally supported to be movablebetween a first latched position and a second unlatched position, a pairof cooperating rollers having their axes parallel spaced relation andbeing free to rotate in opposite directions, a fixed base plate havingupstanding parallel frames extended normal to the axes of said rollersand ovided with parallel spaced guide slots matching the spacing of saidrollers, said rollers being freely rotatively and slidably supported insaid guide slots, said latch lever having an inclined surface engagingone of said rollers, springs operating between said rollers and saidframes biasing said rollers to an extreme position in slots in whichsaid latch lever is in its first latched position, a stopper mounted onsaid base plate and having an inclined surface engaging the other ofsaid rollers, a strip contiguous between said pair of rollers andconnected with a movable armature of a tripping electro-magnet, saidarmature acting to prevent the bias of said rollers from operating saidlatch lever, and said armature operable upon energization of saidtripping electro-magnet to allow one of said rollers to move fromrestraining engagement with said latch lever, whereby the circuitbreaker is allowed to operate by freeing the latch lever to move to itssecond unlatched position.

MASATOSHI KUWAYAMA.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,510, i Henry Sept. 30, 1924 1,799,985 McCoy Apr. 7, 19311,815,637 Viele July 21, 1931 1,953,789 Thumim Apr. 3, 1934

